New built laptop

My brother built a new laptop with a pretty good parts on it. CPU2.53GHz, EXTGfx, 2GB memory, 320GBHDD, Wireless LAN but never finished insatlling OS in it. He left home because he got a big fight with my dad. He haven't called home for a month now and I've tried calling his cell phone but it's been disconnected. He only left me a note saying..."all the hardwares are installed but not configured yet...and no OS installed yet too". I"ve tried to turn it on and it only says "operating system not found". I've tried to install our PC's XP Pro. It start the set-up, showed me different hardwares names but none of them is the same with the hardwares that my brother installed. After a while it stops and gave me an error. I'm not computer savvy and I only know very little about computer and I only know how to use a computer but not to built it. My daddy says he will buy me Vista OS discs but I don't want to waste money buying it if the computer will not work at all. Can anyone give me an advise?